Nowadays, there are backside illumination Complementary Metal-Oxide Semiconductor (CMOS) image sensors with a layer structure (for example, see Patent Document 1). The CMOS image sensor is manufactured in a manner in which a circuit board on which a drive circuit is formed is prepared separately from a sensor board on which an opto-electronic converter is formed, and the circuit board is stuck to a side opposite to the light-receptive surface of the sensor board.
Such a CMOS image sensor is formed into a layer structure in a manner in which the wiring layer surface of the sensor board is connected to the wiring layer surface of the circuit board. The CMOS image sensor is provided with a connection unit to electrically connect the sensor board and the circuit board. In the connection unit, a through-via penetrating the semiconductor layer of the sensor board and connected to the wiring layer of the sensor board is connected to a through-via penetrating the sensor board and connected to the wiring layer of the circuit board by a wiring unit formed on the upper part of the light-receptive surface of the semiconductor layer of the sensor board. A color filter and an on-chip lens for each pixel are provided on the light-receptive surface of the semiconductor layer of the sensor board.
In such a case, the shorter the distance between the color filter and the opto-electronic converter is, the better the sensitivity or the color mixture becomes. For example, in consideration of the limitations due to the circuit wiring or the alignment marks, or in order to loose the stress of the sensor board, it is preferable that the thickness (the length in a direction perpendicular to the sensor board) of the light-receptive surface of the semiconductor layer is thin. Thus, the peripheral area around the wiring unit is thinner than the wiring unit. The wiring unit forms a height difference on the light-receptive surface of the semiconductor layer. As a result, a color filter is unevenly applied on the light-receptive surface after the wiring is formed.
Similarly, when a wiring unit is formed around an area in which pixels are formed on the semiconductor substrate in a solid-state image device such as a front-side illumination CMOS image sensor or a Charge Coupled Device (CCD) image sensor and the wiring unit is thicker than the area, a height difference caused by the wiring unit causes uneven application of a color filter on the surface.